Are there different forms of autism?

Pervasive Development Disorder, or, PDD is a general category of disorders characterized by severe and pervasive impairment in several areas of development including having commonalties in communication and social deficits. (American Psychiatric Association 1994). The DSM-IV is used to diagnose different disorders under the broad heading of PDD and specify which it is. This is done by a large number of the criteria are present, associated specific diagnosis in a category. From here, an evaluation is done by a team of professionals. (Also see Diagnosis). There are five main classifications of PDD, the main difference is how they differ in severity.
"Autistic Disorder
impairments in social interaction, communication, and imaginative play prior to age 3
years. Stereotyped behaviors, interests and activities.

Asperger's Disorder
characterized by impairments in social interactions and the presence of restricted interests
and activities, with no clinically significant general delay in language, and testing in the
range of average to above average intelligence.
Pervasive Developmental Disorder- Not Otherwise Specified
(commonly referred to as atypical autism) a diagnosis of PDD-NOS may be made when
a child does not meet the criteria for a specific diagnosis, but there is a severe and
pervasive impairment in specified behaviors.
Rett's Disorder
a progressive disorder which, to date, has occurred only in girls. Period of normal
development and then loss of previously acquired skills, loss of purposeful use of the
hands replaced with repetitive hand movements beginning at the age of 1-4 years.
Childhood Disintegrative Disorder
characterized by normal development for at least the first 2 years, significant loss of
previously acquired skills. (American Psychiatric Association 1994)"1
It would be wrong to assume that everyone in each one of these categories belong together because they have all the exact same symptoms, for symptoms can be mixed an matched. If you look at the Characteristics of autism, this can be seen clearly. No matter what the severity though, all children can lean to function and be taught productively.